A371054 Numbers whose ternary representation consists of a run of 1's, then a run of 0's, then a run of 2's.

11, 29, 35, 38, 83, 89, 107, 110, 116, 119, 245, 251, 269, 323, 326, 332, 350, 353, 359, 362, 731, 737, 755, 809, 971, 974, 980, 998, 1052, 1055, 1061, 1079, 1082, 1088, 1091, 2189, 2195, 2213, 2267, 2429, 2915, 2918, 2924, 2942, 2996, 3158, 3161, 3167, 3185

Offset: 1

Author

Clark Kimberling, Mar 19 2024

Keywords

• nonn
• base

Comments

a(n) == 2 (mod 3) for all n.

Crossrefs

Cf. A007089, A371055.

Programs

Mathematica

Map[#[[1]] &, Select[Map[{#, Map[#[[1]] &, Split[IntegerDigits[#, 3]]] == {1, 0, 2}} &,
Range[2, 4000, 3]], #[[2]] &]]  (* this sequence *)
ToExpression[Map[IntegerString[#, 3] &, %]]  (* A371055 *)
(* Peter J. C. Moses, Mar 06 2024 *)
Take[With[{nn=6},Flatten[Table[FromDigits[Join[PadRight[{},z,1],PadRight[{},o,0],PadRight[{},t,2]],3],{z,nn},{o,nn},{t,nn}]]]//Sort,50] (* Harvey P. Dale, Mar 29 2025 *)

Python

from itertools import count, islice
def A371054_gen(): # generator of terms
    return (3**(l-a)*(3**a-1>>1)+3**b-1 for l in count(3) for a in range(1,l-1) for b in range(1,l-a))
A371054_list = list(islice(A371054_gen(),20)) # Chai Wah Wu, Mar 20 2024